In the Japanese Pharmacopoeia 15th edition, a burdock fruit is defined as a fruit of burdock, Arctium lappa Linne (Compositae). In addition, a burdock fruit is a herbal medicine prescribed for Gingyo-san, Kufugedoku-to, Shofusan and the like, and is classified into a primary material to be used as a pharmaceutical agent exclusively.
A burdock fruit contains approximately 7% of arctiin which is classified into lignan glycoside and approximately 0.6% of arctigenin which is an aglycone of arctiin.
In recent years, cells derived from pancreas cancer such as PANC-1, AsPC-1, BxPC-1 and KP-3 have strong tolerance to an extreme nutrient starvation state, and the possibility is reported that the elimination of the tolerance may be a new biochemical approach in the cancer therapy (Patent document 1).
It is reported that arctigenin is effective, when screened a material which can release the viability of tumor cells in the undernutrition condition using pancreas cancer cell line PANC-1 (Non-patent document 1). According to the above knowledge, a burdock fruit extract containing arctigenin can be used as an anticancer agent for treating pancreatic cancer.
A burdock fruit which is known currently contains arctigenin at a low content of approximately 0.6%. In addition, it is hard to dissolve in water. Thus, it is extremely difficult to produce a burdock fruit extract containing arctigenin at high content by a conventional hot water extraction method.
In addition, provision of a burdock fruit extract containing a definite content of arctigenin as an active ingredient is desired for use in treatment of pancreatic cancer and the like, however, it is difficult to control the conversion of arctiin into arctigenin so that a definite content of arctigenin which is hard to dissolve in water is contained in the production of the burdock fruit extract containing arctigenin at high content, as described above.
Furthermore, it is found that a burdock fruit extract containing a definite content of arctigenin and arctiin has a particularly excellent anticancer effect when it is used to treat pancreatic cancer and the like. Therefore, a method for production that can control the content of arctigenin and arctiin to a definite content is desired in the production of a burdock fruit extract containing arctigenin at high content. Particularly, a method to make it possible to produce a burdock fruit extract containing arctigenin and arctiin at a weight ratio of approximately 1:1 is desired.